Go from
this to
01. Crop your cap to your liking and then go to Filter > Sharpen >> Unsharp mask... settings: Amount = 50% Radius = 2.0 pixels Threshold = 5 Levels. This will leave you with something that looks like this, this will be your base:
02. Duplicate your base and set to screen at 100%. Repeat this process until you end yp with something that looks like this:
I needed to duplicate my base three times:
This will vary greatly from cap to cap depending on the quality and brightness of your cap so it is a matter of experimenting, some of your screen layers may need to have your opacity lowered.
03. Duplicatte the base and drag it to the top of your other layers, set to Soft Light at 100%.
04. Layer > New Adjustment Layer > Gradient Map...
This screen will pop up:
The gradient will be a combination of whatever colors you currently have selected in set foreground/background color in the tools menu:
Unless these colours are set to black and white you are going to end up with a really strange looking image, like this:
You have two options for fixing this, you can either set the foreground/background colors to black and white (it doesn't matter which is black and which is white) before setting the new adjustment layer.
Or you can double click on the current gradient:
Which will bring up this menu:
Simply click on a black and white gradient and click OK.
Either way after you have a black and white gradient click on OK in the gradient map menu and you will be left with this:
05. Layers > Merge All or Control + Shift + E and you have either a completed icon or a base to work with!
Other icons made using this technique:
...